diff --git a/cryptography/hazmat/bindings/openssl/ecdh.py b/cryptography/hazmat/bindings/openssl/ecdh.py
index adba015..77beb7a 100644
--- a/cryptography/hazmat/bindings/openssl/ecdh.py
+++ b/cryptography/hazmat/bindings/openssl/ecdh.py
@@ -14,7 +14,7 @@
 from __future__ import absolute_import, division, print_function
 
 INCLUDES = """
-#ifdef OPENSSL_NO_ECDH
+#ifndef OPENSSL_NO_ECDH
 #include <openssl/ecdh.h>
 #endif
 """